I can completely understand that its easier to hold your front by email, than having a face to face show down.
He is good at talking people round. He will "reason" bully & dominate with you, till you give in.
This is why, you need your "bubble". In your bubble there is your best dancing music, the sound of the wind, children's laughter, whatever you love best, it smells of cut grass, peaches, cucumber sandwiches & there are your best trusted friends, you are drinking Pims, on the lawn. There is laughter, serenity, & friendship. you have your best memories & photos of your children/Dad/childhood.
Its a place you create for yourself.
In your bubble you are safe, protected & free. no one can enter uninvited, &
Let him harp on, you can look at him with passive benevolence.
Reply with your 5 word max practiced phrases. "It's not what I want", "It doesn't work for me," "You can't rewrite history" "I'll think about it", "I'll ask my SHL", "NO",
"too late for tears" "you are a noxious influence" "happiness cannot be bought",
"everyone will be happier" ......choose your detached tone, & repeat.
Post its are a good idea, write the "5 word bullet list", & stick on bathroom mirror/fridge along with Akire's idea above